microRNA (miRNA) signaling in Alzheimer's disease (AD) Through extensive miRNA- and DNA-based expression array-, LED-Northern-, ELISA, Western-, immunological and bioinformatics-based analysis we have discovered a highly interactive network of NF-kB sensitive, up-regulated pro-inflammatory microRNAs (miRNAs) and their down-regulated messenger RNA (mRNA) targets and the proteins these mRNAs encode in sporadic Alzheimer's disease (AD) brain. The up-regulation of these pathogenic miRNAs and their down-regulated mRNA targets has been further analyzed in stressed human brain cells in primary culture and in 5xFAD amyloid over-expressing transgenic mouse lines. Through miRNA and mRNA abundance analysis, miRNA-mRNA complementarity mapping, association energy (EA) indexing, ELISA and Western analysis we can explain much of the observed neuropathology characteristic of the AD process by analyzing significant disruptions in selective miRNA-mRNA signaling. Our hypothesis is that there exists a small family of at least 6 critical pro-inflammatory miRNAs in AD brains responsible for targeting and down-regulating a group of pathogenic messenger RNA (mRNA) targets responsible for amyloidogenesis, tau pathology and neuroinflammation with accompanying deficits in synaptogenesis, innate- immunity, phagocytosis and a progressive impairment in A?42 peptide clearance. This renewal of our previous 5 year NIA R01 will investigate the integrated actions of this group of 6 pro-inflammatory, pathogenic miRNAs up-regulated in sporadic AD brain, in stressed human brain cells in primary culture in the brains of 5xFAD mice. The 6 up-regulated pro- inflammatory microRNAs to be studied in detail are miRNA-7, miRNA-9, miRNA-34a, miRNA-125b, miRNA-146a and miRNA-155. Stressors will be those encountered as are found in aging AD brain ? these include reactive oxygen species (ROS), the pro-inflammatory cytokines IL-1? and TNF? and A?42 peptides. Specific Aim 1 will analyze the contribution of these factors in moderate-to- advanced sporadic AD and Down's syndrome (DS) brain; Specific Aim 2 will analyze the contribution of these factors in stressed human brain cells, i.e. in neuronal-glial primary cell co- cultures; Specific Aim 3 will analyze the contribution of these factors in 5xFAD amyloid over- expressing transgenic mouse lines. We will specifically accentuate the study of the most up- regulated miRNAs: miRNA-7, miRNA-9, miRNA 34a and miRNA-146a and their targeted disruption of UBE2A (ubiquitin conjugase protein) and TREM2 (triggering receptor expressed in microglial cells) signaling in AD brain, and in in vitro and in vivo AD models. We will also analyze the applicability of selective NF-kB inhibitors and anti-miRNA (AM) strategies in restoring homeostasis in this system. Our long term goal is the therapeutic manipulation of these miRNA-regulated epigenetic pathways to provide an efficacious treatment for the clinical management of AD at an early stage.